1. Field of the Invention
The present invention relates to a gas turbine, more particularly relates to a transition piece outlet structure enabling a reduction of the temperature difference, and a transition piece, a combustor and a gas turbine having the above outlet structure.
2. Description of the Related Art
A gas turbine is a one kind of prime movers which is comprised of a compressor for compressing air, a combustor for generating high pressure and high temperature combustion gas by burning fuel with the compressed air, and a turbine driven by the combustion gas.
It is important to reduce the thermal stress, which acts on the combustor comprised of a nozzle for injecting fuel and a transition piece for supplying exhaust gas to a turbine in order to improve the reliability of the gas turbine.
Therefore, a technique for cooling the combustion chamber of the combustor with steam (see Japanese Patent Publication No. 3110338) and a technique for cooling the transition piece with air (see Japanese Unexamined Patent Publication No. 2-308926) are already proposed.
Further, it is necessary to reduce the radial temperature difference on the flange, which is used for connecting the transition piece to the turbine (see FIG. 12).
Exhaust gas exhausted from the combustor flows through the transition piece, so occurrence of a temperature difference in the flange of the outlet of the transition piece cannot be avoided. Therefore, cracks are liable to occur due to thermal stress in the corners of the transition piece. An increase of the frequency of maintenance and inspection is therefore unavoidable.
An object of the present invention is to provide a transition piece outlet structure able to reduce the temperature difference of a flange formed at the transition piece outlet, and the transition piece, the combustor and the gas turbine providing the above outlet structure.
To attain the above object, according to a first aspect of the present invention, there is provided a gas turbine combustor transition piece outlet structure providing a flange formed at a gas turbine transition piece outlet with a temperature difference reducing means for reducing a temperature difference between an inside and outside of said flange.
Note that the temperature difference reducing means is at least one of a cooling medium channel formed along an inner circumference of said flange, a cooling medium channel formed along a contact surface with an adjoining flange, and a heating medium channel formed along a surface not contacting an adjoining flange.
Further, the cooling medium is any of compressed air, low temperature steam, or fuel, while the heating medium is any of a combustion gas or high temperature steam.
In the present invention, the temperature difference from the inside to the outside of the flange of the transition piece outlet is reduced.